SECTIONAL TRANSACTIONS.— G. 303 



load capacity of 500 or more tons, concerns closely all newer countries in which, being 

 mainly agricultural, the demands for transport are too intermittent to justify more 

 intensive railways or roadways. 



Where, say, 10s. is available for the transport of maize to a market, then if the 

 transport cost is Is. a ton-mile the maize can be grown economically up to 10 miles 

 from the market ; but if 6d. a ton-mile, up to 20 miles away, the area of the circle 

 around the market within which the maize can be profitably grown being thus not 

 doubled but quadrupled. 



Porterage, 5s. to Is. 6d. per ton-mile ; pack animals, 5s. to 2s. ; bullock wagons, 

 Is. 6d. to 9d. ; mechanical vehicles carrying 1 to 3 tons, 2s. to Is. These costs by 

 these minor means compare with 2d. roughly by rail ; moreover, the expense of the 

 damage to routes by bullock- wagons, and in the case of mechanical vehicles with 

 small load capacity, the cost of road construction or repair does not appear in these 

 costs. 



There is thus a gap in the transport system between the mechanical vehicle with 

 a daily ton-mile capacity of under 100 and the railway train with a like capacity of 

 150,000. This cannot be bridged economically by wheeled vehicles with load 

 capacities of 5 to 15 tons, chiefly because these transmit too high a pressure to the 

 ground, and thus destroy the surface. 



There is eveiy hope, however, that this gap may be bridged by the roadless train 

 on the lines of a vehicle having an average speed of 5 miles per hour, a turning radius 

 of 100 feet, a drawbar pull enabling the vehicle to cope, fully laden, with gradients 

 up to 1 in 15, and the capacity to negotiate water up to 4 feet in depth. Each of 

 the four trailers to be of 25 tons capacity, and mounted on girder tracks having a 

 remarkable road-rolling effect. The tractor to weigh about 25 tons, to be equipped 

 with a Diesel engine of 300 to 400 h.p., and mounted on tracks of special design to 

 give the adhesion necessary for the drawbar pull required, the joints of these tracks 

 embodying a novel principle of construction consisting in the use of rubber in com- 

 pression, thus dispensing with the wear and tear previously experienced in the use 

 of the pin-joint. No part of the vehicle to impose upon the ground a greater pressure 

 per square inch than 12 lbs. It is estimated that the cost of transport by this roadless 

 train could be reduced to 2Jrf. or 2d. a ton-mile. 



The alternative of the multi-wheeled road train is mechanically possible, but 

 objections to this type are : — the high first and maintenance cost ; the loss of power 

 involved in the transmission of the drive from one end of the train to the other, the 

 high pressures transmitted to the ground by the wheels ; even if these pressures be 

 reduced by multiplication of the wheels there still remains the absence of a flat surface 

 of contact with the ground. 



Dr. C. V. VON Abo. — Some Engineering Problems of the South African 

 Railways and Harbours. 



Mr. M. M. LouBSER. — Engineering Problems (Mechanical) in connection 

 with the 3 ft. Q in. gauge, South African Railways. 



Friday, July 26. 



Prof. A. E. Snape. — University Training in Structural Design and Practice. 



Mr. J. C. Hawkins.—^ Review of Irrigation in South Africa. 



JOHANNESBURG. 

 Wednesday, July 31. 



Hon. Sir Charles Parsons, O.M., K.C.B., F.R.S. — Recent Progress in 

 Steam Turbine Plant. 



The paper briefly describes the early history of the steam turbine in South Af ri ca 

 from the beginning of the century and contemporary with notable advances in turbine 

 construction in England. Reference is made to the influence of the industrial 



